Ashley Graham was already 5’9″ and a size 12 by middle school, which led to plenty of bullying from her classmates. But she says their taunts were nothing compared to what she would hear from agents and stylists as a model in New York City.

Graham, 30, was discovered in a Kansas mall near her hometown at age 12, at the same time she had classmates picking on her for being “the big friend with cottage cheese thighs,” she tells PEOPLE.

At 17, after doing local photoshoots, she moved to New York in the hopes of turning modeling into a career. But she encountered resistance over her body type from many of the people in the modeling world.

“I had people on set, like photographers, stylists and even my own agents telling me that I was getting too big,” Graham says. “Or they’d make snide comments like ‘time to put the Snickers down.’ And that is really what stuck with me and was super hurtful.”

A year in to modeling, she gained “25 or 30 lbs.,” and started to question what she was doing.

“It just hit me, like, these people are telling me that I’m fat, I’ve gained weight, and now my career is going to be over. What do I do?” Graham says. “And really, I wanted to give up. I didn’t know how to fix anything.”

She credits her mom, Linda, for getting her through.

“The only person that helped me get out of that rut was my mom,” Graham says. “She told me that I was good enough. She told me that I had to stay, that I had to figure it out. And I’m really glad she did, because a little bit of tough love is what got me through.”

Graham learned how to boost her confidence with daily affirmations, and started telling herself “I am bold, I am brilliant, I am beautiful” in the mirror each morning, which she continues to do today.

“I think our words have power, and if you’re constantly telling yourself that you’re not good enough and you’re doubting your exterior on a daily basis, then that’s what your life going to turn out to be,” she says. “Using affirmations changed my outlook on life.”

With her confidence solidified, Graham moved to IMG Models, and discovered better opportunities than ever, with agents who put her up for Sports Illustrated and more.

“It was just a matter of working with people who can foresee a greater possibility for you,” she says. “I tell this to people all the time: Don’t be afraid to ask for help. Don’t be afraid to go out and if you have a crazy dream, don’t think it’s not going to happen. Did I ever think I was going to have my own British Vogue cover or be on the cover of American Vogue with all the other supermodels? No way! But because I believe in myself and because I work really hard, I got what I wanted and now I feel like the possibilities are endless.”

The modeling industry is now a different world, thanks to Graham, who broke through long-held size barriers. Though she humbly chalks the change up to “timing.”

“Women just really want to see themselves represented,” Graham says. “They want to see age, they want to see size, they want to see race, they to see the diversity of who they are, because we aren’t all these picture-perfect idealized images of beauty that the media and fashion have told us that we are.”

For more on Ashley Graham, pick up this week’s issue of PEOPLE, on newsstands Friday

But she adds that there’s plenty more that needs to happen to diversify the industry.

“What I really want to see, and what I know will be a done deal and it will change, is that we won’t have to talk about size on a runway, size in a campaign, size on a cover, and it’s just the norm,” she says. “We’re not talking about it like this new, wild concept that we put a size-16 girl on the cover of something. That’s really what I want.”

And one more, big thing.

“Studies show that we have 200 years to go until we reach gender equality. That is entirely too long, girl,” Graham says. “That is entirely too long and we should be having it right now.”